For valves which are intended to be used to regulate the flow rate of liquid or gaseous fluids, and where additional functions beyond an ON/OFF function are required, an actuator must be able to assume any desired position within a maximum stroke in a core guiding tube in a reliably reproducible way and within short time. In this process, any occurring friction and the resulting “stick-slip” effect, with larger static friction as compared to dynamic friction, is particularly disruptive. A reliable regulation of the flow rate is not ensured any more in this case.
This is why valves are of interest in which the actuators can be moved by a driving element in a friction-free manner. A known possibility is to use flat springs as guiding elements.
A regulating valve is known from EP 1 536 169 in which the core is guided at its two ends by two flat springs with minimum radial clearance in the core guiding tube along the entire stroke in a non-contact and hence friction-free manner.
Eliminating the friction, however, implies a reduction of damping action of an oscillatory system including a valve armature and flat springs, making it easier to perform excitable vibrations. Such excitations may be caused by sound waves, for example, generated at elevated pressures behind a valve seat where gas expands and compression shocks occur as a rule. In case these sound waves are partially reflected at downwardly (outside the valve) located flow resistance elements (restrictor elements, line connections etc.), resonance phenomena and an associated excitation of undesired vibrations of the core may occur. In this case, regulating the flow rate is not possible any more.